This invention relates to a spread spectrum communication system of a direct sequence type.
Spread spectrum communication systems are explained in various documents such as "Spread Spectrum Systems, Second Edition" written by R.C. Dixon and published from John Wiley & Sons, Inc., in 1984.
In some of conventional spread spectrum communication systems of a direct sequence type, a transmitter includes primary and secondary modulators. The primary modulator modulates a carrier with an information signal and thereby derives a primary modulation signal. The secondary modulator modulates the primary modulation signal with spread codes and thereby derives a secondary modulation signal (a spread spectrum signal). The spread spectrum signal is transmitted from the transmitter to a receiver of the conventional communication systems. The receiver includes a spread code generator generating spread codes which correspond to the spread codes used in the transmitter. The receiver also includes a despreading circuit which despreads the spread spectrum signal with the spread codes to recover a primary modulation signal from the spread spectrum signal. In the receiver of the conventional communication systems, the spread code generator tends to be complicated.